OBJECTIVES: To estimate drug acquisition cost savings comparisons for managed care organizations (MCOs) with availability of generic simvastatin and pravastatin in the US. METHODS: A deterministic study ascertained potential cost savings for MCOs with availability of generic simvastatin and pravastatin. The study focused on patients requiring less substantial cholesterol reduction (<30% LDL-C reduction). National statin prescription sales (November 2004- October 2005) were obtained; dose interchange table was developed identifying statin switches providing LDL-C lowering effect within 10% of the entry drug. The study assumed all patients requiring an LDL reduction of <30% would switch from other equivalent statin doses to simvastatin 5 mg or pravastatin 10 mg daily. Two assumptions with four cost scenarios for generic simvastatin and pravastatin prices were tested: 15% rebate for branded statins, 50% discount rate for generics, and $5 generic and $15 brand co-payments (assumption 1) or 15% rebate for branded statins, 60% discount rate for generics, and $10 generic and $20 brand co-payments (assumption 2). Sensitivity analyses varying discount rates and co-payments for generic products were performed. RESULTS: Total baseline costs to MCOs for branded statins were $0.88B (assumption 1) and $0.80B (assumption 2) for patients eligible to switch to generic simvastatin and $0.78B and $0.69B, respectively, for patients eligible to switch to generic pravastatin. Switching patients to generic simvastatin lowered total costs to $0.53B and $0.32B, providing cost savings for TPPs of $0.36B and $0.48B. Switching patients to generic pravastatin changed total costs to $0.81B and $0.55B, generating cost expenditures of $0.03B and cost savings of $0.15B, respectively. CONCLUSION: With varying assumptions in the study, switching patients requiring less substantial cholesterol reduction to generic simvastatin generated substantial cost savings compared to generic pravastatin. Extended studies focusing on economic impacts on MCOs are encouraged to evaluate cost savings following availability of other generic and combination statin drugs.